Imprinting

Some preliminary notes

Most of the advice about hand-rearing orphaned owls sounds a warning about the danger of imprinting. A found chick is assumed to become an "imprinted owl", or an "imprint", after a couple of days in captivity, especially if hand-fed. It's made pretty clear that this means psychologically damaged in some bad and irreversible way. The owl even comes to think it's a human. Such owls, goes the script, are completely unfit for release. Unable to fend for themselves they will die, or pester humans for food. So, it is implied, if you pick up and keep an owl chick, far from doing good you are doing something morally reprehensible. In a word, it's a crime against wildlife.

This has me really puzzled! Most tawny chicks found on the ground are 15-20 days old, and my (limited) experience with chicks of this age has been that imprinting doesn't happen. If it does, it's so superficial that it's hardly a cause for concern. Others are now publishing results that point to the same conclusion. The British RSPCA and the Hawk Conservancy Trust report that hand-reared tawny orphans do as well on release as wild-fledged owlets (for details see reports in the Accipiter on my Tawny Owl links page). Accounts of the release of other owl species are limited, but so far they present a similar picture. So we seem to have a big contradiction between the claims about imprinting and the evidence. It looks like a subject that's worth examining further.

A Great Horned Owl

Max R. Terman, in Messages from an Owl, has quite a lot to say on the subject. The owl was Stripey, an orphan Great Horned Owl which became the subject of a study by one of his research students. The relevance of this study is that its main purpose was the thorny question of imprinting. Could an imprinted owl be successfully returned to the wild? There were to be no half-measures -- to achieve this aim the young owl had to be deliberately (over) exposed to humans:

With Stripey perched contentedly in a large aquarium . . . Pete and I sat in my office planning his future. The idea was to rear this owl with maximum human contact, then release him and keep tabs on his activity through telemetry. I warned Pete: "You'll almost have to live with Stripey -- feeding him, touching him, and basically substituting yourself for his mother. We must be certain that he has adequate opportunity to identify with humans." (Messages p. 9)

In fact after a few weeks of Pete, Terman himself became pretty much the surrogate parent when he took Stripey from the lab back to his own home on a Kansas farm. There he quickly became, by his own admission, thoroughly attached to the personable young owl. The owl was released after some training in rodent capture and with the option to return for supplementary food placed in a "feeding station". She, for Stripey was a she, left the immediate area of the homestead in stages. Her progress in the wild was monitored over several years by radio-tagging, so she could be found at any time.

Terman's conclusion is that the owl's ability to survive after release "was not all that hampered by being hand reared. Why then are there so many horror stories about imprinted owls?" (p.144, my emphasis). And, more specifically, "My experiences with Stripey have raised my doubts about the conventional wisdom of the proponents of imprinting" (pp. 145-6). I may not be from Missouri, he says, but I want to see the evidence (my paraphrase of comments on pp.145 and 152). But evidence of what? The problem is that the book is in fact rather ambivalent on the matter of Stripey's imprinting -- for example both there and elsewhere Terman refers to Stripey as an "imprinted owl". From a wider reading of the book it seems that Terman accepts the common view that she must have been imprinted but concludes that with her carefully supervised release it did her prospects little harm. My own reading of his detailed account of the owl's behaviour is that the simple and obvious explanation could just as well be that she wasn't imprinted, and that what we're looking at is another account of a human-reared bird that's relying on a mix of intelligence and instinctual behaviour in making the transition to surviving in the wild without guidance from natural parents. Nowhere does the author suggest that the owl sought guidance from him, or that Stripey had a mistaken species image -- i.e. thought she was a human -- despite her carefully human-orientated upbringing. Basically, after some initial orientation and hesitation, Stripey made off, did her own thing and avoided her former "parent". I don't think it misrepresents the book to say that this research project showed not so much that Stripey managed despite being imprinted as that there was little, if any, imprinting in the first place. Terman's ambivalence on the question seems to arise from the fact that he feels uncomfortable at rejecting completely such a widely accepted notion as owl imprinting.

Look at it another way: why shouldn't it be supposed that there's a perfectly natural stage of filial dependence which we all -- owls, other animals and humans -- go through and which we all equally naturally emerge from whether the parent is a natural parent or a foster parent of whatever species? This does not necessarily have to involve such a strong or specific concept as imprinting. If I had been Terman this would have been my "null hypothesis" -- the hypothesis to start from and accept or reject on the basis of the evidence before moving on to more specialised hypotheses such as imprinting. Nothing I see in the book suggests much else than a youngster asserting its independence with increasing confidence as it gains experience of its new environment. It's difficult to see any scientific justification for invoking the concept of imprinting.

More on Stripey at a later date as this is a hugely relevant and well-documented case. There's a nice pic of Terman with his owl on my website here. Stripey, released in 1988, was still around in 2005. There's an update on her here: Hillsboro Free Press 19 Jan 2005. As of January 2008 there's no suggestion on Terman's own website that Stripey's not still alive and well.

And a Barrred Owl

There's another detailed account of the release of a hand-reared owl in Tree Child, a 19-page story on The Owl Pages. Here the orphan is a Barred Owl. What is interesting is that in this case every possible rule was broken! Not only was Sushi, the owlet, treated rather like a human child and spoiled rotten, but until it could fly it was kept all day in the foster mother's upholstery shop. Here it was able to watch, and sometimes interact with, the owner, the staff, and any customer who dropped by. According to the imprinters this should have been a recipe for total and utter disaster! In their books Sushi would have been unreleaseable. In fact Sushi made a smooth and uneventful transition into the wild, found a mate, and settled in an area away from her human foster parents. Interestingly, too, almost no effort was needed to teach Sushi to hunt. A "killing box" was used, but no teaching was needed -- the owl knew what to do almost from the start. I've found the same with young tawnies. As concluded in an RSPCA report on the outcome of releasing hand-reared Tawny Owls, "The recovery of several pellets confirmed that hunting in this species is an innate process." The experience with Stripey and Sushi suggests that it may be in other owl species too. (A killing box was used with Stripey, but Terman doesn't suggest that his owl didn't know what to do, just that her pouncing accuracy with the fleeing mice needed practice.)

My own birds

I can add from my own experience with keeping several birds (not just owls) from an early age that the relationship they develop with you is very similar and in its "emotional" aspects is largely determined by them. I think many people who keep birds would be surprised to hear them described as imprints when these owners' day to day experience is of quite fiercely independent creatures who do what they want. These birds' behaviour shows little evidence of being governed by some affective drive like imprinting on a human. The main problem facing an orphaned owl on release is learning survival skills -- finding food and avoiding danger -- in the absence of parents. Of course this means it has to wean itself off dependence on a human for food, but if you release a young tawny you'll be disappointed if you expect it to behave like an imprinted or even half-tame bird and fly back to you! Interestingly, I have seen a form of imprinting in a young pigeon I kept for some years. In the classification below this would have been called sexual -- he used to bring objects from a nest he'd made and bury them in my ear -- but after a while he made the intelligent decision that this was a waste of time. Again, he was in control of the nature of his relationship with me. Sophie, the orphan owl in my care at the moment, also has her own mind and prefers to be left to bum around on her own. She doesn't like me interfering with her activities -- and lets me know! Generally she moves away from me, not towards me. Once every few days she may land on my shoulder to say hello with a nibble around the ear, but soon she's off again to pursue her own interests.

The types of imprinting

The understanding of imprinting has moved on since Konrad Lorentz famously (re)discovered it with his goslings. Lorentz maintained that imprinting happened during the first day after hatching (the "critical period") and that it was irreversible. The process actually turns out to be fuzzier than that. A good brief summary by a researcher who spent many years studying the phenomenon can be found here: Professor Howard S. Hoffmann on imprinting.

There appear to be four types of imprinting in birds: filial, the following response, the classic imprinting of newly hatched birds on the mother; auditory, response to the mother's call; sexual, youngsters identify the proper species (their own!) for future mating (this happens in the first two weeks after hatching; and habitat, whereby the young remember their birth habitat and seek a similiar area for their own nesting. (From "Make Way! Why ducklings follow their mother wherever she goes", by Eldon Greij, Birder's World, February 2004.)

A critical concept -- the sensitive period

It is generally accepted that imprinting occurs during a "sensitive period", and that during this period there is a time when the animal is especially susceptible known as the "critical period". The sensitive period for filial imprinting in newly hatched birds is variously given as 12 to 24 or 48 hours. The proponents of imprinting thus have an immediate difficulty in that most orphan owls are found quite a long time after (usually two to three weeks) the sensitive period for filial imprinting, when the possibility of such imprinting on a human would be impossible as the young owl has already identified its mother and father as its true parents.

What we are then left with, if the distinctions are correct, is sexual imprinting, which involves the acquisition of a correct species image. This, we are told, happens in the first two weeks of life, so once again we are left with a difficulty as most orphan owls are found when they are older than this. Personally I find the evidence that's advanced for misplaced species image unconvincing -- owls attempting to mate with the gloved hand or a person's head. Many bird owners report this behaviour by pet birds which clearly have a correct species image as they are kept with other birds, and this mating behaviour may be done with any suitable object! My own pigeon did it regularly (on the hand), and I know for a fact that he had a correct species image. He was reared by his parents in my flat for the first weeks of his life and subsequently had every opportunity to identify himself with his own kind. He saw other pigeons every day, used to display to himself in front of a mirror, and responded appropriately to films of pigeons on my computer.

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As a next step in this piece on imprinting I need to find out exactly what imprinted behaviour looks like -- what should be looked for as indisputable evidence that imprinting has occurred. For example, should we expect to see owlets following a human foster parent like ducklings? This could be quite tricky as after his first time out Terman's owl Stripey was so depressed by mobbing birds that he/she "literally came running to me and leaped onto my arm. Cuddling him, I returned him to the barn. As he snuggled against my chest, I could almost believe the experts". (Messages p. 20.) Case closed, the imprinters might say. But they need to read on. I've a suspicion the situation is going to be complicated by responses like this early behaviour by Stripey! An understandable move by an intelligent bird . . . or a mere mechanistic reponse by an imprinted owl?

Before I get round to continuing the piece, here are some web pages on imprinting -- there's not much out there unfortunately. And below the rule, some more illustrative bits and pieces.

Learning who is your mother: The behavior of imprinting, by Silvia Helena Cardoso and Renato Sabbatini.

Wikipedia entry for Imprinting (fairly basic).

An interesting illustration, or the owl that voted with its wings

On The Owl Pages there's a short (true) story that's given as an illustration of what NOT to do if you find a downed tawny chick. The immediate point is that if you pick one up you don't take it home and leave it on a branch hoping it'll be fed. So far so good.

But the second part of the tale of this little rescuee, Eric, brings up the notion of imprinting. It fell to the author to take the owl into his care. On the very first encounter, at the place where the original finders had brought him in, he "had to force feed him, thus imprinting him". Phew, just like that. One thing led to another, and "As he was imprinted we got him registered with the Department of the Environment and started to train him up for display". Eric was with the writer for seven years, though despite the imprinting he admits that "the wild side showed".

One night, while being fed, Eric escaped and fled. When he reappeared a week later Eric had a female in tow. Now remember, an owl imprint is supposed to think it's human, and to seek the company of humans. So was this some pretty little human girl who flew to perch beside Eric? What an enchanting tale that would make.

What's so funny about this story is that it's put up in part as a cautionary tale about imprinting, but that it in fact shows precisely the opposite. Eric knew what he was and where he wanted to be, even after seven years in captivity as a display owl. After all this time he even managed to fish some inborn knowledge about how to hunt from a corner of his clever little head. If Eric's story doesn't tell us something about the widely held notion of imprinting I don't know what does.

Eric's story on The Owl Pages is here

And an illustration from bird-rearing

Some time ago I met a lady who breeds African Grey parrots to supplemement her income. She lives in a caravan surrounded by bird cages, and just inside the door a small room is crammed with incubators, electronic gear to control the temperature and humidity, and equipment for feeding very young birds. To sell her parrots this lady has to rear birds that are hand-tame, and to do this she knows from experience that the hatchlings mustn't be allowed near a mother bird for one moment. If the new-born chick sees a parrot mother, that's it, the chick will imprint and the young bird will be difficult to keep as a pet. So that's what the incubators are for -- the eggs are taken away from the mother and incubated artificially. That way the hatchling never sees a mother parrot. The lady told me that it's the only way you can rear African Greys to be accustomed to the hand. Bird owners will know that many birds freak when a human hand comes near them.

This is far more in line with the real scientific meaning of imprinting, in this case "filial" imprinting. The owl foundlings that are brought in aged between 2 and 3 weeks have long ago imprinted on an owl mother. So what are we looking at with "imprint" owls? I suggest that it means no more than what you'd see in many animals that have become used to having humans around and being fed by them. Dogs, well, they're slightly different perhaps, but we'd hardly refer to a cat or a cow as an "imprint".

Of course I'm not saying that imprinting doesn't exist, and I'm not saying either that captive owls don't become tame and dependent, or that on occasions a released captive or pet owl will seek out humans for food. What I am saying is that it looks as though to apply the term to such owls is, to adapt an advertising slogan, the misappliance of science. It may be that a healthy appliance of Occam's razor is called for and that simpler, more everyday, even obvious interpretations are needed. Not least that human-habituated owls are capable of behaving quite intelligently and not because they think they are humans or in response to some unconscious drive that was originally intended to be used for a distinct and well-defined set of behaviours.

In a word, time for a little common sense combined with a little observation of how birds actually behave.

Coming next:

Ollie the owl: crazed human imprint . . . or just a tame, and rather hungry, ex-pet?

Photo and story in Telegraph & Argus 27 November 2007 on this page. Location is Bingley, Yorkshire.

The human experience of imprinting (an intuitive way in)

I can't write with any kind of a scientific hat on here, but I bet I'd be correct if I said that the various human experiences of bonding relied on exactly the same neural pathways in the same parts of the brain as imprinting in animals. But bonding's a nicer word than imprinting, so it's used to maintain and respect the illusion that we're somehow not connected to animals, or, to be more precise, that our experience and behaviour mark a fundamental discontinuity with the evolutionary past. The belief that we're a "separate creation" is a cultural thing, and not always easy to free oneself of.

"Bonding" is a warm word, implying the involvement of emotion, and even intelligence and/or free will. "Imprinting" is a cold word implying the workings of mechanism and instinct.

My guess is that we humans undergo very much the same type of imprinting as animals: certainly filial and sexual. Filial imprinting, or bonding, is something of course that most of us emerge from easily enough as we move from infancy through childhood to adolescence. So why isn't it obvious to those who argue for imprinting in young birds that filial imprinting has its time — that it's a phase the growing bird emerges from naturally. Yet the filial imprinting of a young bird on a human is spoken of as though it were permanent.

In fact it looks as though humans are subject to forms of imprinting that animals are not. One type that immediately comes to mind could be called "svengali" imprinting: what you see in fundamentalist religious communities, or with charismatic political leaders.

So we are actually quite well placed to understand imprinting.

(Page revised January 2008)

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